It's not like flipping a switch. You will have occasional breakthroughs, but you will also have plateaus where you feel like you're getting worse. This is a general guideline of what you'll learn.
White: basic positions and movements
Blue: beginning familiarity with most (nearly all) positions and movements, especially defense
Purple: beginning mastery of select techniques, increased offensive capability, more risk-taking (which means you'll get "caught" more)
Brown: like a purple belt but the belt is ugly, better at more stuff with fewer holes, likely able to convey why what you're doing is dumb
Black: like a brown belt but more handsome and chicks now think it's cool you waste all your free time rolling around with dudes, has seen enough stupid shit that it no longer bothers you